The present invention relates to electrical bushings. More particularly, the present invention relates to gas filled bushings for introducing high voltage conductors into a housing, such as a gas filled circuit breaker.
In bushings of the foregoing type, the central conductor serves both a mechanical and electrical function. In addition to providing an electrical connection between the conductive flanges on either side of the hollow dielectric housing, the conductor provides the mechanical connection for holding the bushing together. In order to be certain that the central conductor serves both functions properly, it is necessary to design the bushings to accommodate relative expansion or dimensional changes between the metallic central conductor and the porcelain insulative housing due to thermal expansion and contraction. This is a major problem since bushings of the present type are ordinarily subjected to wide ranges of temperatures and since the coefficients of thermal expansion of the metallic conductor and porcelain housing are quite divergent.
The standard solution of this problem has been to provide a spring assembly connecting the central conductor to one of the two conductive flanges. Bushings of this type are illustrated in U.S. Pat. No. 3,566,001 and will be described in some detail with reference to FIG. 1, below.